Effects of excipients on the interactions of self-emulsifying drug delivery systems with human blood plasma and plasma membranes.

Due to its versatility in formulation and manufacturing, self-emulsifying drug delivery systems (SEDDS) can be used to design parenteral formulations. Therefore, it is necessary to understand the effects of excipients on the behavior of SEDDS formulations upon parenteral administration, particularly their interactions with blood plasma and cell membranes. In this study, we prepared three neutrally charged SEDDS formulations composed of medium-chain triglycerides as the oil phase, polyoxyl-35 castor oil (EL35) and polyethylene glycol (15)-hydroxystearate (HS15) as the nonionic surfactants, medium-chain mono- and diglycerides as the co-surfactant, and propylene glycol as the co-solvent. The cationic surfactant, didodecyldimethylammonium bromide (DDA), and the anionic surfactant, sodium deoxycholate (DEO), were added to the neutral SEDDS preconcentrates to obtain cationic and anionic SEDDS, respectively. SEDDS were incubated with human blood plasma and recovered by size exclusion chromatography. Data showed that SEDDS emulsion droplets can bind plasma protein to different extents depending on their surface charge and surfactant used. At pH 7.4, the least protein binding was observed with anionic SEDDS. Positive charges increased protein binding. SEDDS stabilized by HS15 can adsorb more plasma protein and induce more plasma membrane disruption activity than SEDDS stabilized by EL35. These effects were more pronounced with the HS15 + DDA combination. The addition of DDA and DEO to SEDDS increased plasma membrane disruption (PMD) activities, and DDA (1% w/w) was more active than DEO (2% w/w). PMD activities of SEDDS were concentration-dependent and vanished at appropriate dilution ratios.

Mucolytic self-emulsifying drug delivery systems (SEDDS) containing a hydrophobic ion-pair of proteinase.

AIM: The aim of this study was to form hydrophobic ion-pairs of proteinase with cationic surfactants and to incorporate them into self-emulsifying drug delivery systems (SEDDS) to improve their mucus permeating properties. METHODS: Proteinase was ion-paired with benzalkonium chloride (BAK), hexadecylpyridinium chloride (HDP), alkyltrimethylammonium bromide (ATA) and hexadecyltrimethylammonium bromide (HDT) at pH 8.5-9.0, and subsequently incorporated into SEDDS consisting of Cremophor EL, propylene glycol, and Capmul 808-G (40/20/40). Mucus permeation of SEDDS containing proteinase complexes was evaluated via rotating tube technique and cell-free Transwell® insert system. Additionally, enzymatic activity of proteinase complexes as well as their potential cytotoxicity was evaluated. RESULTS: Among all tested hydrophobic ion-pairs, proteinase/BAK showed highest potential. Mucus diffusion of SEDDS containing proteinase/BAK complex yielded in 2.3-fold and 2.5-fold higher mucus permeability with respect to blank SEDDS at Transwell® insert system and rotating tube technique, respectively. Furthermore, proteinase/BAK complex maintained the highest enzymatic activity of 50.5 ± 5.6% compared to free proteinase. At a SEDDS concentration as low as 0.006% cell viability was just 80%. The addition of proteinase complexes to SEDDS increased cytotoxicity on Caco-2 cells in a concentration-dependent manner. CONCLUSION: SEDDS loaded with proteinase/BAK complexes are promising nanocarriers because of enhanced mucus permeating properties.

Self-emulsifying drug delivery systems and cationic surfactants: do they potentiate each other in cytotoxicity?

OBJECTIVES: The aim of this study was to evaluate the cytotoxicity of self-emulsifying drug delivery systems (SEDDS) containing five different cationic surfactants. METHODS: Cationic surfactants were added in a concentration of 1% and 5% (m/m) to SEDDS comprising 30% Capmul MCM, 30% Captex 355, 30% Cremophor EL and 10% propylene glycol. The resulting formulations were characterized in terms of size, zeta potential, in-vitro haemolytic activity and toxicity on Caco-2 via MTT assay and lactate dehydrogenase release assay. KEY FINDINGS: The evaluated surfactants had in both concentrations a minor impact on the size of SEDDS ranging from 30.2 ± 0.6 to 55.4 ± 1.1 nm, whereas zeta potential changed significantly from -9.0 ± 0.3 to +28.8 ± 1.6 mV. The overall cytotoxicity of cationic surfactants followed the rank order: hexadecylpyridinium chloride > benzalkonium chloride > alkyltrimethylammonium bromide > octylamine > 1-decyl-3-methylimidazolium. The haemolytic activity of the combination of cationic surfactants and SEDDS on human red blood cells was synergistic. Furthermore, cationic SEDDS exhibited higher cytotoxicity of Caco-2 cells compared to SEDDS without cationic surfactants. CONCLUSIONS: According to these results, SEDDS and cationic surfactants seem to bear an additive up to synergistic toxic risk.

Thiomers: Impact of in situ cross-linkers on mucoadhesive properties.

The aim of this study was to evaluate the impact of in situ cross-linkers on the gelling and mucoadhesive properties of thiomers. Polycarbophil-cysteine conjugate (PCP-cys) was synthesized by covalent attachment of l-cysteine to polycarbophil via amide bond formation mediated by 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride (EDAC) and N-hydroxysuccinimide (NHS) whereas in situ cross-linkers (PAA-cys-MNA) were synthesized by the same bond formation between poly(acrylic acid) (PAA) of 2.1-, 6-, and 15kDa and 2-((2-amino-2-carboxyethyl)disulfanyl)nicotinic acid (cys-MNA) used as ligand. The in situ cross-linking properties were studied via rheological measurements of dynamic viscosity of mixtures of PCP-cys and PAA-cys-MNA with purified porcine intestinal mucus and via rotating cylinder method. The diffusion of polymers in purified porcine intestinal mucus was studied via rotating tube technique. The results showed that in situ cross-linkers (PAA 2.1-, 6-, 15kDa) increase the dynamic viscosity of PCP-cys/mucus mixtures by 5.1-, 5.6-, and 3.5-fold. Combinations of 10% of in situ cross-linkers PAA 2.1-, 6- or 15kDa and 90% PCP-cys increased the adhesion time 1.1-, 2.0- and 4.9-fold, respectively, compared to PCP-cys alone. Diffusion study showed that low molecular mass PAAs highly penetrate into the mucus gel layer due to their high polymer chain mobility compared to PCP-cys. The results provide evidence for the potential of in situ cross-linking agents as gelling and mucoadhesion enhancers.

Storage Stability of Bivalirudin: Hydrophilic Versus Lipophilic Solutions.

It was the aim of this study to incorporate a model peptide bivalirudin in self-emulsifying drug delivery system (SEDDS) and compare its storage stability with conventional aqueous solutions. Firstly, bivalirudin lipophilicity was increased via hydrophobic ion pairing using anionic or cationic surfactants. The chosen bivalirudin docusate complex (BIV/AOT) was incorporated into SEDDS composed of 40% (w/w) Cremophor EL, 20% (w/w) Capmul PG-8, and 40% (w/w) propylene glycol with a drug payload of 0.20% (w/w). SEDDS were stable over a wide pH range for at least 7 days at 37°C and showed an immediate bivalirudin release profile. Moreover, aqueous bivalirudin solutions were shown to be most stable between apparent pH 3 and 4. Furthermore, 94.39% and 72.66% of bivalirudin in SEDDS and 10% propylene glycol, respectively, remained intact after 90 days of storage at 25°C ± 2°C, whereas 99.12% and 80.54% were still intact in SEDDS and 10% propylene glycol at 5°C ± 3°C, respectively. Bivalirudin in reconstituted commercially available product Angiomax® was, however, long-term unstable. According to these findings, SEDDS could be considered as a potential bivalirudin stabilization medium against chemical degradation.

Improved mucoadhesive properties of self-nanoemulsifying drug delivery systems (SNEDDS) by introducing acyl chitosan.

This study was aimed to improve the mucoadhesive properties of SNEDDS by the incorporation of acyl chitosan including octanoyl chitosan (OC), lauroyl chitosan (LC) and palmitoyl chitosan (PC). SNEDDS and acyl chitosan SNEDDS were characterized regarding droplet size and zeta potential. Their mucoadhesivity on porcine intestinal mucosa was evaluated by falling liquid film technique using Sudan Red G as marker. Degree of substitution of chitosan was determined to be 52.8%, 64.8 and 48.5% for OC, LC and PC, respectively. SNEDDS and acyl chitosan SNEDDS displayed a droplet size less than 50nm and 80-300nm as well as a zeta potential of -0.2 to -1.6 and 0.05 to 0.99mV, respectively. Introducing 2% acyl chitosan into SNEDDS increased the residence time of SNEDDS on intestinal mucosa 2-fold. It is concluded that due to the incorporation of acyl chitosan into SNEDDS, their mucoadhesive properties can be increased.

Self-emulsifying drug delivery systems (SEDDS): Proof-of-concept how to make them mucoadhesive.

AIM: The objective of this study was to provide a proof-of-concept that self-emulsifying drug delivery systems can be made mucoadhesive by the incorporation of hydrophobic mucoadhesive polymers. METHODS: In order to obtain such a hydrophobic mucoadhesive polymer, Eudragit® S100 was thiolated by covalent attachment of cysteamine. After determination of the thiol group content, in vitro mucoadhesion studies (rotating cylinder and rheological measurements) were performed. Then, synthesized conjugate was incorporated into self-emulsifying drug delivery systems (SEDDS) and their toxic potential as well as that of unmodified and thiolated Eudragit® S100 was examined on Caco-2 cell line. Lastly, the mucoadhesiveness of developed SEDDS on porcine intestinal mucosa was determined. RESULTS: Generated thiolated Eudragit® S100 displaying 235±14µmol of free thiol groups and 878±101µmol of disulfide bonds per gram polymer showed a great improvement in both: dynamic viscosity with mucus and adhesion time on mucosal tissue compared to the unmodified polymer. Resazurin assay revealed that unmodified and thiolated polymers and also SEDDS dispersions were non-toxic over Caco-2 cells. Furthermore, the incorporation of 1.5% (w/w) of such thiomer into SEDDS led to remarkably improved mucoadhesiveness. Blank SEDDS were completely removed from the mucosa within 15min, whereas >60% of SEDDS containing thiolated Eudragit® S100 were still attached to it. CONCLUSION: These results provide evidence that SEDDS can be made mucoadhesive by the incorporation of hydrophobic mucoadhesive polymers.

Preactivated thiolated pullulan as a versatile excipient for mucosal drug targeting.

AIM: The purpose of the present study was to generate a novel mucoadhesive thiolated pullulan with protected thiol moieties and to evaluate its suitability as mucosal drug delivery system. METHODS: Two different synthetic pathways: bromination-nucleophilic substitution and reductive amination including periodate cleavage were utilized to synthesize such thiolated pullulans. The thiomer (pullulan-cysteamine) with the highest amount of free thiol groups was further enrolled in a reaction with 6-mercaptonicotinamide and its presence in pullulan structure was confirmed via NMR analysis. Furthermore, unmodified, thiolated and preactivated thiolated pullulan were investigated in terms of mucoadhesion via rotating cylinder studies and rheological synergism method as well as their toxicity potential over Caco-2 cells. RESULTS: Comparing both methods the reductive amination seems to be the method of choice resulting in comparatively higher coupling rates. Using this procedure pullulan-cysteamine conjugate displayed 1522±158µmol immobilized thiol groups and 280±70µmol free thiol groups per gram polymer. Furthermore, 82% of free thiol groups on this conjugate were linked with 6-mercaptonicotinamide (6-MNA). The adhesion time on the rotating cylinder was up to 46-fold prolonged in case of the thiolated polymer and up to 75-fold in case of the preactivated polymer. Rheological measurements of modified pullulan samples showed 98-fold and 160-fold increase in dynamic viscosity upon the addition of mucus within 60min, whereas unmodified pullulan did not show an increase in viscosity at all. Both conjugates had a minor effect on Caco-2 cell viability. CONCLUSION: Because of these features preactivated thiolated pullulan seems to represent a promising type of mucoadhesive polymers for the development of various mucosal drug delivery systems.

Development and in vitro evaluation of zeta potential changing self-emulsifying drug delivery systems for enhanced mucus permeation.

The aim of this study was the development of zeta potential changing self-emulsifying drug delivery systems (SEDDS). Various cationic surfactants were incorporated into a formulation consisting of 30% Cremophor EL, 30% Capmul MCM, 30% Captex 355 and 10% propylene glycol (w/w). A substrate of intestinal alkaline phosphatase (IAP), 1,2-dipalmitoyl-sn-glycero-3-phosphatidic acid sodium (PA), was thereafter incorporated into SEDDS. Size, zeta potential and polydispersity index were determined. Phosphate release studies were performed using three different models, namely, isolated IAP, Caco-2 cell monolayer and rat intestinal mucosa and the amount of released phosphate was quantified by malachite green assay. Interaction of SEDDS and mucus was investigated regarding surface charges and mucus diffusion studies were performed using rotating tube technique. SEDDS were diluted 1:100 in 100mM HEPES buffer and a negative zeta potential was obtained. By addition of isolated IAP, 15% to 20% phosphate was liberated from SEDDS within 3h and a shift of zeta potential from negative to positive was observed. On Caco-2 cell monolayer and rat intestinal mucosa, 12% and 23% phosphate were released, respectively, from SEDDS diluted 1:1000 in glucose-HEPES buffer. Positively charged droplets were bound to negatively charged mucus resulting in a decrease of zeta potential, whereas negatively charged SEDDS showed no interaction. Furthermore, negatively charged SEDDS diffused faster through mucus layer as higher extent of incorporated Lumogen was present in deeper mucus segments in comparison to positively charged ones. Accordingly, zeta potential changing SEDDS provide an effective mucus permeation combined with higher cellular uptake when droplets reach absorptive epithelium membrane.

Development and in vitro evaluation of an oral SEDDS for desmopressin.

CONTEXT: Self-emulsifying drug delivery systems (SEDDS) are among most promising tools for improving oral peptide bioavailability. OBJECTIVE: In this study, in vitro protective effect of SEDDS containing desmopressin against presystemic inactivation by glutathione and α-chymotrypsin was evaluated. MATERIALS AND METHODS: The partitioning coefficient (log P) of desmopressin was increased via hydrophobic ion pairing using anionic surfactants. Solubility studies were performed to select the appropriate solvents for SEDDS preparation. Subsequently, droplet size and emulsification properties of 22 SEDDS formulations were evaluated. Moreover, the peptide-surfactant complex was dissolved in two chosen SEDDS formulations. Finally, SEDDS containing desmopressin were characterized regarding lipase stability, toxicity, and in vitro protective effect toward glutathione and α-chymotrypsin. RESULTS: Desmopressin log P was increased from initial -6.13 to 0.33 using sodium docusate. The resulting desmopressin docusate complex (DES/AOT) was incorporated in two different SEDDS formulations, containing Capmul 907 P as main solvent. DES/AOT-SEDDS-F4 (containing 0.07% w/w DES/AOT) was composed of 50% Capmul 907P, 40% Cremophor RH40, and 10% Transcutol. The comparatively more hydrophilic formulation DES/AOT-SEDDS-F15 (containing 0.25% w/w DES/AOT) consisted of 20% Capmul 907P, 40% Acconon MC8-2, and 40% Tween 20. Both formulations were stable toward digestion by lipase and protected desmopressin toward α-chymotrypsin degradation. Moreover, DES/AOT-SEDDS-F4 also protected the peptide from thiol/disulfide exchange reactions with glutathione and was not cytotoxic at a concentration of 0.375% (w/w). CONCLUSION: DES/AOT-SEDDS-F4 protected desmopressin from in vitro glutathione and α-chymotrypsin degradation. DES/AOT-SEDDS-F4 was metabolically stable and nontoxic. Therefore, it could be considered as a potential delivery system for oral desmopressin administration.

Development and in vitro characterisation of an oral self-emulsifying delivery system for daptomycin.

It was the aim of this study to develop an oral self-emulsifying drug delivery system (SEDDS) for the peptide drug daptomycin exhibiting an anionic net charge. Drug lipophilicity was increased by hydrophobic ion pairing with cationic surfactant dodecylamine hydrochloride in molar ratio of surfactant to peptide 5:1. Log P (octanol/water) of -5.0 was even raised to +4.8 due to complexation with dodecylamine hydrochloride. Various SEDDS formulations were developed and characterised regarding emulsification properties, droplet size, polydispersity index and zeta potential. When the daptomycin dodecylamine complex (DAP/DOA) was dissolved in a formulation containing 35% Dermofeel MCT, 30% Capmul MCM and 35% Cremophor RH40, a maximum payload of even 8.0% (w/w) corresponding to 5.5% pure daptomycin was achieved. The formulation was degraded by lipase within 90min. Release studies of daptomycin from this formulation emulsified in 50mM phosphate buffer pH6.8 demonstrated a sustained drug release for at least six hours. Moreover, SEDDS exhibited also mucus permeating properties as well as a protective effect towards drug degradation by α-chymotrypsin. According to these results, SEDDS containing 8% DAP/DOA complex may be considered as a new potential oral delivery system for daptomycin.